Recipient Organization
UNIVERSITY OF CALIFORNIA, IRVINE
(N/A)
IRVINE,CA 92697
Performing Department
(N/A)
Non Technical Summary
Humans face significant health and food security risks from heavy metals such as arsenic and lead. Food crops grown in soils with high levels of these toxic metals--whether due to natural occurrence at high levels in soil or proximity of farm to heavy metal sources--can absorb them, causing them to accumulate in the edible plant parts and ultimately contaminate the food made from those parts. As a result, research is needed to create effective techniques to minimize the accumulation of heavy metals in food crops during cultivation, with the ultimate aim of reducing the risks to human health.The primary goal of this research project is to create safe and sustainable soil amendments that can selectively bind to arsenic and lead in soil, thereby preventing their uptake by plants during cultivation. The soil amendments will be made from nanosized iron particles, which can react with and bind to arsenic and lead. The particles will be tailored to improve their capacity to bind to arsenic and lead in soil, prevent the release of the bound arsenic and lead as plants grow in soil, and allow for the recovery of the amendments and bound arsenic and lead from soil. The performance of the soil amendments will be evaluated in a series of greenhouse and field studies, using widely consumed food crops. This project will address the problem of arsenic and lead in food, improve food safety and security, and contribute to sustainable agriculture.
Animal Health Component
70%
Research Effort Categories
Basic
30%
Applied
70%
Developmental
0%
Goals / Objectives
The overall goal of this research project is to create iron-based nanosized soil amendments that can effectively immobilize arsenic and lead in soil through multiple mechanisms. The ultimate aim is to use the soil amendments to prevent the uptake of the heavy metal(loid)s during food crops cultivation without compromising plant health and productivity. An accomplishment of the overarching goal of this project would have a significant impact by decreasing the uptake of soil arsenic and lead by food crops, which would in turn benefit the health of Americans, especially young children. In addition, it would decrease food recalls due to elevated arsenic and lead content, and preserve the income of farmers. This project supports the effort of the United States Department of Agriculture (USDA), which is collaborating with the Food and Drugs Administration (FDA) on the "Closer to Zero" initiative, to consider how plants uptake metals from soil and determine how to mitigate heavy metals uptake by plants. These goals will be achieved through four specific objectives:Synthesis and characterization of nano-amendments, evaluation of their lead and arsenic immobilization performance in soil, and determination of the influence of root exudates on immobilization performance.Conducting mechanistic studies to determine the arsenic and lead sequestration efficacy of nano-amendments during the cultivation of food crops in greenhouse studies.Validation of the efficacy of selected nano-amendments for arsenic and lead sequestration at field scale.Modeling of experimental results to predict arsenic and lead, and nano-amendment fate using ChemFate, and efficacy of nano-amendments using machine learning.
Project Methods
Nano-amendment synthesis and characterization: Iron-based nanoparticles will be prepared via reduction of iron ions with sodium borohydride. A precursor of sulfur will be included for sulfidized iron particles. Tetraethyl orthosilicate (TEOS) will be used for silica coating and its porosity will be ensured with cetyltrimethylammonium bromide (CTAB). The nano-amendments will be characterized for their size and morphology using scanning and transmission electron microscopy (SEM and TEM). Their elemental composition at the surface and bulk will be determined using energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The crystal phase structure will be analyzed by X-ray diffraction (XRD), while X-ray photoelectron spectroscopy (XPS) will used to analyze the surface element composition and valence. Fourier transform infrared spectroscopy (FTIR) will be used to characterize the functional groups on the surface of the nano-amendments while their surface area will be evaluated by the Brunnauer-Emmett-Teller (BET) method. The magnetic properties of the nano-amendments (coercivity, magnetization and retentivity) will also be measured. These properties will be correlated with the metal immobilization performance of nano-amendments. Relating the structure of nano-amendments with their efficacy provides a pathway for improving their performance.Arsenic and lead immobilization in bare soil studies: Immobilization of arsenic and lead in soils by the different variants of the nano-amendments will be studied using batch studies. Three soils will be obtained from the CAES experimental farms--Lockwood farm in Hamden CT, the Valley Laboratory in Windsor, CT, and the Griswold Laboratory in Griswold, CT--for this study. The nano-amendments will be thoroughly mixed into arsenic- or lead-contaminated soils, and bioavailable arsenic or lead will be determined over time. To determine how root exudates impacts arsenic and lead immobilization/ remobilization, which has not been previously studied, exudates will be extracted from a plant and amended into plant-free contaminated soils that are treated with the nano-amendments. For all studies, we will investigate mechanisms of immobilization and remobilization using analytical tools like X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The data obtained from these studies will be used to shortlist the highest-performing nano-amendments for the cultivated soil studies.Arsenic and lead immobilization in cultivated soil studies: These studies aim to confirm the efficacy of the selected nano-amendments for immobilizing arsenic and lead when plants are growing in soil. In these studies, we will also determine whether remobilization of immobilized arsenic and lead occurs, and how nano-amendment dose and treatment time influences phyto-uptake of arsenic and lead. Bioaccumulation of arsenic and lead will be determined in root and shoot tissues. Physiological, biochemical, and molecular endpoints will also be investigated, including biomass, transpiration and photosynthesis, oxidative stress, total protein, glutathione levels, and amino acids, tissue elemental composition and nutrient content, plant tissue metabolomics and RNA analysis. Soil microbial community will also be profiled to determine impacts of nano-amendments on the soil microbiome. We will begin with greenhouse studies, and the results will be validated with field studies at the three CAES experimental farms. At the end of these studies, the safest and most effective nano-amendments will be identified.Modeling approaches: Experimental data will be used to adapt a model, ChemFate, for predicting the fate of arsenic, lead, and nano-amendments in soil. The model will help us to understand the way the nano-amendments and metallic contaminants change and move in soil over a long time. In addition, artificial neural network (ANN) will be used to develop a mathematical relationship between the treatment conditions (e.g., nano-amendment dose, soil pH, treatment time, etc.) and efficacy of nano-amendments. Efficacy of nano-amendments is defined as reduction in phyto-uptake of arsenic and lead due to their application, relative to plants grown in untreated, contaminated soils. Using ANN, we can identify the properties of soil and nano-amendments that have the highest influence on arsenic and lead immobilization in soil, which can be used to further optimize the performance of the nano-amendments.